Rudolf Jäger

Recommendation index for DVB content using Service information

This paper presents algorithms and techniques to generate recommendations for DVB content. The developed recommendation engine uses metadata which are delivered by the DVB transport stream, the Service Information. The creation of user profiles, which contains the preferences of an individual user, is described. Personalization strategies, to filter the interesting contents for each user, will be shown. Furthermore new developed and firstly presented algorithms to generate recommendations for DVB content are listed and described. A PPG (Personal Program Guide), which has been developed to visualize the recommendations is shown, too. Several tests show the usefulness of the developed recommendation scheme.

QoSiLAN - A Heterogeneous Approach to Quality of Service in Local Area Networks

Since most real-time audio and video applications lack Quality of Service (QoS) support and QoS-aware networkhardware is not common in consumer grade networks, theQuality of Experience (QoE) of, for example, high definitionInternet Protocol Television (IPTV) is very limited. Therefore, this paper proposes a novel approach for enabling QoS in unmanaged, heterogeneous Local Area Networks (LAN) across access technologies. To support QoS in LANs, especially in the home’s environment, the QoSiLAN system enables selforganised QoS, implemented in the hosts, rather than modify the protocol stack. In contrast, traditional solutions rely on network support by switches, access points or routers. Perlink resource reservation and prioritisation are achieved by knowledge of the topology map and by reducing the bandwidth of disturbing best effort traffic caused by other communicating hosts. Since QoSiLAN follows a layer 3 QoS model, it qualifies for LANs with mixed access technologies.

Security Analysis of the Micro Transport Protocol with a Misbehaving Receiver

BitTorrent is the most widely used Peer-to-Peer (P2P) protocol and it comprises the largest share of traffic in Europe. To make BitTorrent more Internet Service Provider (ISP) friendly, BitTorrent Inc. invented the Micro Transport Protocol (uTP). It is based on UDP with a novel congestion control called Low Extra Delay Background Transport (LEDBAT). This protocol assumes that the receiver always gives correct feedback, since otherwise this deteriorates throughput or yields to corrupted data. We show through experimental investigation that a misbehaving uTP receiver, which is not interested in data integrity, can increase the bandwidth of the sender by up to five times. This can cause a congestion collapse and steal large share of a victims bandwidth. We present three attacks, which increase the bandwidth usage significantly. We have tested these attacks in a real world environment and show its severity both in terms of number of packets and total traffic generated. We also present a countermeasure for protecting against the attacks and evaluate the performance of that defence strategy.

Who Is Going to Be the Next BitTorrent Peer Idol

Active measurement studies show that the Peer-to-Peer (P2P) file sharing protocol Bit Torrent is highly under attack. Moreover, malicious peers can easily exploit the original seeding algorithm and therefore reduce the efficiency of this protocol. In this paper, we propose a novel seeding algorithm that requests peers to vote for their best sharing peers. Our results show that this incentive mechanism makes Bit Torrent harder to exploit without losing performance. In some situations our algorithm even outperform other seeding algorithms. The peer exchange - that comes as a side effect - reduces the dependency on a centralized tracker and increases the robustness and the efficiency. We studied the effectiveness of our approach in a real testbed comprising 32 peers.

Stealing Bandwidth from BitTorrent Seeders

BitTorrent continues to comprise the largest fraction of Internet traffic. While significant progress has been made in understanding the BitTorrent choking mechanism, its security vulnerabilities have not been investigated thoroughly. This paper presents an experimental analysis of bandwidth attacks against different choking algorithms in the BitTorrent seed state. We reveal a simple exploit that allows malicious peers to receive a considerably higher download rate than contributing leechers, therefore introducing significant efficiency degradations for benign peers. We show the damage caused by the proposed attack in two different environments: a lab testbed comprising 32 peers and a PlanetLab testbed with 300 peers. Our results show that 3 malicious peers can degrade the download rate up to 414.99% for all peers. Combined with a Sybil attack that consists of as many attackers as leechers, it is possible to degrade the download rate by more than 1000%. We propose a novel choking algorithm which is immune against bandwidth attacks and a countermeasure against the revealed attack.

Poster: Destabilizing BitTorrent's clusters to attack high bandwidth leechers

BitTorrent protocol incentivizes sharing through its choking algorithm. BitTorrent choking algorithm creates clusters of leechers with similar upload capacity to achieve higher overall transfer rates. We show that a malicious peer can exploit BitTorrents choking algorithm to reduce the upload utilization of high bandwidth leechers. We use a testbed comprising of 24 nodes to provide experimental evidence of a distributed attack in which the malicious peers increase the download time for high bandwidth leechers by up to 16% and increases average download time of the swarm by up to 15% by using distributed and loosely-coupled malicious peers which comprise only 4.7% of the swarm. The countermeasures of this attack are a part of our ongoing research work.

Autonomous QoS management and policing in unmanaged local area networks

The high increase of bandwidth-intensive applications like high definition video streaming in home and small office environments leads to QoS challenges in hybrid wired/wireless local area networks. These networks are often not QoS aware and may contain bottlenecks in their topology. In addition, they often have a hybrid nature due to the used access technology consisting of, for example, Ethernet, wireless, and PowerLAN links. In this paper, we present the research work on a novel autonomous system for hybrid QoS in local area networks, called QoSiLAN, which does not rely on network infrastructure support but on host cooperation and works independently of the access technology. We present a new QoS Signalling Protocol, policing and admission control algorithms, and a new lightweight statistical bandwidth prediction algorithm for autonomous resource management in LANs. This new QoS framework enables link based, access-medium independent bandwidth management without network support. We provide evaluation results for the novel bandwidth prediction algorithm as well as for the QoSiLAN framework and its protocol, which highlight the features, robustness, and the effectiveness of the proposed system.

Recommendations in a heterogeneous service environment

This paper presents novel algorithms which are able to generate recommendations within a heterogeneous service environment. In this work explicitly set preferences as well as implicitly logged viewing behavior are employed to generate recommendations for Digital Video Broadcast (DVB) content. This paper also discusses the similarity between the DVB genres and YouTube categories. In addition it presents results to show the comparison between well known collaborative filtering methods. The outcome of this comparison study is used to identify the most suitable filtering method to use in the proposed environment. Finally the paper presents a novel Personal Program Guide (PPG), which is used as a tool to visualize the generated recommendations within a heterogeneous service environment. This PPG is also capable of showing the linear DVB content and the non-linear YouTube videos in a single view.